Various different flat panel displays including plasma display panels (PDP) and liquid crystal displays (LCD) available in the market do not come with an identical light emitting capability of the three primary colors: red, green and blue after the flat panel displays are assembled, due to the deviation among the materials of the flat panel displays. These flat panel displays show different color characteristics which means that if no special color correction is taken place in the production process, these flat panel displays will have different color appearances for the same input signals. As a result, manufacturers cannot be sure that every produced flat panel display can come out with the same colors. Even in a batch of products of the same brand produced by the same manufacturing process, a consistency of color appearance cannot be achieved, and thus manufacturers usually perform a correction for the color characteristics (such as color temperature, gray scale, and white balance) of the assembled flat panel displays before they are shipped.
At present, the methods of correcting the color characteristics of the flat panel displays are divided into two major types, and the first type primarily uses an external characterization function in an open color management system (CMS), and the system adopts the concept of a color profile (which describes the characterization function) to convert the same input signal into another specific file to be displayed through corresponding color profile, so that flat panel displays with different color characteristics can come out with the same colors, and thus the color profile is provided for describing a function f( ) or an inverse function f−1( ) of the existing relation between an input signal RGB and its corresponding color output CIE colorimetric signal XYZ of every flat panel display as shown below:XYZ=f(RGB), orRGB=f−1(XYZ)
The system cannot correct a flat panel display to standard color characteristics, but it uses a color conversion engine to convert the original input file into another file then to be shown as specific color characteristics for different flat panel displays, and thus the system basically does not correct any color characteristic of the flat panel display. The system only describes the color display characteristics of the flat panel display by the color profile, and it is considered as color correction by external characterization engine. The color management system of this sort requires an additional memory device installed on each flat panel display or its controller for storing corresponding color profiles, such that when an original input file is received, a color conversion engine is used to correct the original input file and generate a corresponding color correction file according to the characteristics function in the color profile, and then output the color correction file temporarily stored in the memory device, so as to appear the expected color for each flat panel display. Since the system needs to perform the processes of converting, storing, and outputting when the input file is received for each time, therefore the system consumes more processing time which is inapplicable for a flat panel display (such as a television) that needs to display a huge number of instant images.
The second type is a closed color correction system which corrects the color characteristics of a flat panel display directly into certain specific color characteristics, such that when the same file is inputted, each flat panel display can show the same color appearance. When the input file in compliance with a standard specification (such as sRGB or NTSC), the flat panel will display it in compliance with the standard set forth by the specification. Traditionally, a color correction is performed by using an instrument to measure color temperature and color shift when the flat panel display shows a white color, and then manually adjusting the gain and offset of the three primary colors: red, green and blue, until the white color displayed by the flat panel display approaches target color temperature and within certain color deviation, such that the flat panel displays so produced have correct parameters including color temperature, gray scale and white balance to show the best color appearance. However, such method for manually calibrating the parameters including color temperature, gray scale and white balance not only consumes much time and efforts, but also causes inevitable discrepancies between the measured parameters of the flat panel display and the ideal parameters due to human errors occurred in the manual calibration process and causes an unstable quality of the products.
To save time and labor cost and expedite the calibration of parameters including color temperature, gray scale and white balance, it is usual to calibrate the parameters including color temperature, gray scale and white balance of a flat panel display in a batch of shipment, and use the corrected values of the three primary colors: red, green and blue so obtained as a basis to calibrate other flat panel displays in the same batch of shipment and save the values in an internal memory of the corresponding flat panel displays. In other words, the correction data, like gain and offset of the flat panel displays in the same batch of shipment are set as the same values. Although such calibration method saves a great deal of time and labor cost and expedite the calibration of color temperature, gray scale and white balance of the flat panel display, it cannot give consideration to the difference of color characteristics among various flat panel displays nor avoid sacrificing the color accuracy for each flat panel display. As a result, only one set of flat panel display can have the best color appearance, but the rest of flat panel displays cannot achieve the best color appearance.
To solve the aforementioned problem, many manufacturers examine the original color characteristics of every flat panel display and obtain corrected color characteristic values for correcting each flat panel display, such that the flat panel displays have standard color characteristics after the flat panel displays are assembled. The most common way is to adopt the concept of “gamma characteristic correction” to correct errors of color characteristics of each flat panel display as disclosed in U.S. Pat. No. 5,796,384, and compute the corrected color characteristic values and record the corrected values in a non-volatile memory such as a flash RAM in a hardware circuit of the flat panel display or a rewriteable memory device as shown in FIGS. 1 and 2, and its manufacturing procedure is described briefly as follows:                (200) Complete assembling all components of a flat panel display 10, wherein a main board (which is a video system board) 11 of the flat panel display 10 has a controller 12;        (201) Use a signal generating device to generate an input signal (which is a video signal), and output the signal to the flat panel display 10;        (202) Use a color measurement instrument 13 to examine the output value of the panel 14, and analyze the color characteristics;        (203) Obtain corresponding corrected color characteristic values needed in a gamma correction circuit for the flat panel display 10 to display the target output value through the computation of an inverse function between the input signal and the output value according to a set specification; and        (204) Download the corrected color characteristic values into a non-volatile memory 16 of the controller 12 through a transmission interface 15, and use the corrected color characteristic values as the permanent recorded values.        
Therefore, the correction circuit can perform the color correction, but such approach needs to install additional electronic components (such as a non-volatile memory 16) on each flat panel display 10 or its controller 12, not only incurring a higher manufacturing cost, but also consumes more manufacturing time and labor in the manufacturing procedure, since it is necessary to download the corrected color characteristic values into the non-volatile memory 16 of the controller 12 through the transmission interface 15 to complete the correction of color characteristics.